1. Field of the Invention
The present invention generally relates to a process for the ammoxidation or oxidation of a saturated or unsaturated hydrocarbon to produce an unsaturated nitrile or an unsaturated organic acid.
The invention particularly relates to a process for the gas-phase conversion of propane to acrylonitrile and isobutane to methacrylonitrile (via ammoxidation) or of propane to acrylic acid and isobutane to methacrylic acid (via oxidation).
2. Description of the Prior Art
Mixed metal oxide catalysts have been employed for the conversion of propane to acrylonitrile and isobutane to methacrylonitrile (via an ammoxidation reaction) and/or for conversion of propane to acrylic acid (via an oxidation reaction). The art known in this field includes numerous patents and patent applications, including for example, U.S. Pat. No. 5,750,760 to Ushikubo et al., U.S. Pat. No. 6,036,880 to Komada et al., U.S. Pat. No. 6,043,186 to Komada et al., U.S. Pat. No. 6,143,916 to Hinago et al., U.S. Pat. No. 6,514,902 to Inoue et al., U.S. Patent Application No. US 2003/0088118 A1 by Komada et al., U.S. Patent Application No. 2004/0063990 A1 to Gaffney et al., and PCT Patent Application No. WO 2004/108278 A1 by Asahi Kasei Kabushiki Kaisha
Although advancements have been made in the art in connection with catalysts containing molybdenum, vanadium, antimony and niobium effective for the conversion of propane to acrylonitrile and isobutane to methacrylonitrile (via an ammoxidation reaction) and/or for the conversion of propane to acrylic acid and isobutane to methacrylic acid (via an oxidation reaction), the catalysts need further improvement before becoming commercially viable. In general, the art-known catalytic systems for such reactions suffer from generally low yields of the desired product.
Tellurium can become volatile at the temperatures used for the ammoxidation of propane and isobutane and/or for the conversion of propane to acrylic acid and isobutane to methacrylic acid (via an oxidation reaction). Catalysts containing relatively high amounts of tellurium have exhibited a loss of tellurium during the ammoxidation or oxidation operation. Catalyst performance can be negatively impacted by the loss of tellurium.